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Effect of the four gradient playback buttons drawn using javascript and HTML5 Canvas

Source: Internet
Author: User
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Comments: This article mainly introduces the effect of the four gradient playback buttons drawn by using javascript and HTML5 Canvas. For more information, see

<Canvas> </canvas> is a new tag in html5. Like all dom objects, it has its own attributes, methods, and events. There is a plotting method, js can call it for plotting. In this article, the canvas label and Javascript are used together to draw a playback button with a four-color gradient effect ,:

Implementation Code:


The Code is as follows: <! Doctype html>
<Html>
<Head>
<Meta http-equiv = "Content-Type" content = "text/html; charset = gbk">
<Title> draw button </title>
</Head>
<Body>
<Canvas id = "myCanvas" width = "600" height = "400"> your browser does not support Canvas. Please upgrade your browser! </Canvas>
<Script type = "text/javascript">

Var canvas = document. getElementById ('mycanvas ');/* Get the defined canvas */
Var ctx = canvas. getContext ('2d ');/* painting in a two-dimensional environment */
DrawPlayButton (ctx, 200,200 );
DrawPlayButton (ctx, 400,200 );
DrawPlayButton (ctx, 300,200 );
Function drawPlayButton (_ context, x, y ){
Var nRadius = 30; // radius
_ Context. save ();
_ Context. translate (x, y );
// Constructor
Var yellowGrad = _ context. createLinearGradient );
YellowGrad. addColorStop (0, '# fccb02 ');
YellowGrad. addColorStop (0.5, '# fbf14d ');
YellowGrad. addColorStop (1, '# ffcb02 ');
Var blueGrad = _ context. createLinearGradient (30, 0, 0, 30 );
BlueGrad. addColorStop (0, '# 2a459c ');
BlueGrad. addColorStop (0.5, '# 0e7ads ');
BlueGrad. addColorStop (1, '# 2a459e ');
Var redGrad = _ context. createLinearGradient (,); // rotate by rotate
RedGrad. addColorStop (0, '# d0372f ');
RedGrad. addColorStop (0.5, '# e0675e ');
RedGrad. addColorStop (1, '# ce392d ');
Var greenGrad = _ context. createLinearGradient (30,0,); // rotate by rotate
GreenGrad. addColorStop (0, '#059700 ');
GreenGrad. addColorStop (0.5, '#02e003 ');
GreenGrad. addColorStop (1, '#019a02 ');

// Draw the angle between two arcs
DrawCake (_ context, 0, yellowGrad, nRadius );
DrawCake (_ context, Math. PI/2, blueGrad, nRadius );
DrawCake (_ context, Math. PI, redGrad, nRadius );
DrawCake (_ context, 3 * Math. PI/2, greenGrad, nRadius );
// Incircle color
Var lingrad = _ context. createLinearGradient (-30,-30,30, 30 );
Lingrad. addColorStop (0, '# 4672df ');
Lingrad. addColorStop (0.2, '#6188e5 ');
Lingrad. addColorStop (0.5, '# 98b1ef ');
Lingrad. addColorStop (0.8, '# b1c3f2 ');
Lingrad. addColorStop (1, '# eaedfc ');
_ Context. save ();
_ Context. beginPath (); // incircle
_ Context. fillStyle = lingrad;
_ Context. arc (, nRadius-10, 0, Math. PI * 2, true );
_ Context. fill ();
_ Context. closePath ();
_ Context. restore ();
// Draw a triangle
Var trianglerad = _ context. createLinearGradient (-6,-10,-6, 10 );
Trianglerad. addColorStop (0, '# 99d4ea ');
Trianglerad. addColorStop (0.2, '# 5e8fdd ');
Trianglerad. addColorStop (0.5, '#0f17a1 ');
Trianglerad. addColorStop (0.8, '# 4c65cc ');
Trianglerad. addColorStop (1, '#7299e5 ');
_ Context. beginPath ();
_ Context. fillStyle = trianglerad;
_ Context. moveTo (12, 0 );
_ Context. lineTo (-6, 10 );
_ Context. lineTo (-6,-10 );
_ Context. fill ();
_ Context. restore ();
}
// Draw a slice
Function drawCake (_ context, _ nRotateAngle, _ fillColor, _ nRadius ){
_ Context. save ();
_ Context. beginPath ();
_ Context. fillStyle = _ fillColor;
_ Context. rotate (_ nRotateAngle );
_ Context. moveTo (_ nRadius-10, 0 );
_ Context. lineTo (_ nRadius, 0); // draw a line to the right
_ Context. arc (0, 0, _ nRadius, 0, Math. PI/2, false );
_ Context. lineTo (0, _ nRadius-10); // draw
_ Context. arc (, _ nRadius-10, Math. PI/, true); // draw the Inner arc counterclockwise
_ Context. fill ();
_ Context. closePath ();
_ Context. restore ();
}
</Script>
</Body>
</Html>


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Related Keywords:
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